Nathan Adrian finished fourth in his first event since being diagnosed with testicular cancer and undergoing two surgeries, swimming the 100m freestyle at the Tyr Pro Series in Bloomington, Ind., on Friday.

Adrian, who captured the 2012 Olympic 100m free among five career golds, clocked 49.31 seconds to finish .55 behind winner Zach Apple. Adrian, 30, announced Jan. 24 that he was diagnosed with testicular cancer. It was caught early, and the prognosis was good.

“It’s a good feeling,” Adrian said on Olympic Channel: Home of Team USA. “It’s tough to describe, right? This is home for me. Honestly, I’ve never been to Bloomington, but this environment. … That’s what feels right.”

It’s just the beginning of what should be a busy season. Adrian plans to swim the 4x100m free at the world championships in July and race individually at the Pan American Games the following week.

Come next summer, Adrian will likely need to break 49 seconds to make a fourth straight Olympic team and get under 48 to swim the individual 100m free in Tokyo.

“You get something like an adverse health diagnosis, everything kind of stops,” Adrian said. “You realize health is No. 1, and everything had to be pushed to the side. Fortunately, we’re through that for now, and I get to do what I can to get back on track.”

In other events Friday, Katie Ledecky won the 400m freestyle in 3:59.95, the second-fastest time in the world this year. Australian 18-year-old Ariarne Titmus swam 3:59.66 at her national championships last month. Ledecky owns the 12 fastest times in history, including the world record of 3:56.46 from Rio.

Olympic and world champion Simone Manuel took the women’s 100m free in 53.65, topping Mallory Comerford by .46. Ledecky, who doesn’t swim the 100m free internationally, was fourth.

Manuel remains ranked 10th in the world this year, while Australian Cate Campbell has been a half-second faster than anyone else.

Olympic and world champion Lilly King clocked the world’s fastest 100m breaststroke of 2019, a 1:05.68 to knock Russian rival Yulia Efimova off the top of the world rankings. King swam for the first time as a pro following a decorated career in Bloomington at the University of Indiana.

Fellow former Hoosier Cody Miller won the men’s 100m breast in 59.24, his fastest time since the 2017 World Championships. Miller, the Olympic bronze medalist, was slowed by a knee injury last year, when he failed to qualify for this year’s world championships. His time on Friday, which beat national champion Michael Andrew, would have won the 2018 U.S. title.

IRVINE, Calif. — Not too long ago, Katie Ledecky was the teen phenom in the pool. Now, after finishing her nationals slate with a third convincing win, her threats ahead are all younger than she is.

Ledecky prevailed by 3.12 seconds in the 400m freestyle on Saturday night and scratched out of her last event, Sunday’s 1500m freestyle. Don’t worry, she is still eligible to swim the 1500m free at this year’s major international meet, the Pan Pacific Championships in Tokyo in two weeks.

Australian distance phenom AriarneTitmus, 17, will be there. The Tasmania native lowered her personal bests in the 200m, 400m and 800m frees by more than three seconds each since 2017 Worlds (but is still two seconds slower than Ledecky in the 400m free this year, and 12 seconds slower in the 800m free).

Taylor Ruck will also be in Tokyo. The 18-year-old Canadian ranks second to Ledecky in the 200m free this year, just .25 behind (followed by Titmus, .29 behind).

Ruck has taken more than three seconds off her 200m free personal best in the last year. She will join Ledecky at Stanford in the fall (though Ledecky has turned pro and won’t compete for the Cardinal).

Ledecky has never lost a major international meet final to a younger swimmer. It doesn’t look likely to happen in two weeks, but she may never be the youngest woman on the podium again.

“I guess it’s a little different, but I think I have the benefit of knowing … what it’s like to have somebody in mind that you’re chasing,” said Ledecky, who notably beat reigning Olympic 800m free champion Rebecca Adlington at her first Games as a 15-year-old in 2012. “I know that there are a lot of great swimmers out there that are chasing me. That motivates me just as much as chasing someone motivated me when I was 15.”

Nationals conclude Sunday, live on Olympic Channel: Home of Team USA at 9 p.m. ET.

In other events Saturday, Olympic and world champion Lilly King won the 100m breaststroke in 1:05.36, a time that trails only Russian rival Yulia Efimova this year.

Olympic champions Ryan Murphy and Matt Grevers went one-two in the men’s 100m back in 52.51 and 52.55, the two fastest times in the world this year. They shared the podium at 2017 Worlds behind Chinese winner Xu Jiayu.

Michael Andrew, who turned pro at 14 in 2013, won his first national title in an Olympic event, taking the men’s 100m breast in 59.38 seconds. Olympic bronze medalist Cody Miller was sixth and will not swim at Pan Pacs or the 2019 Worlds.

Zane Grothe repeated as U.S. men’s 400m free champion. The 26-year-old clocked 3:46.53, edging Grant Shoults by .37. Grothe was seventh at the 2017 World Championships and ranks 10th in the world this year.

“[Eleven] months after Rio, it’s going to be so hard to get back what I had in Rio, but I’m more than happy to come here, defend my title, or attack my title,” Peaty said on the BBC. “Year after year, we’re going to find bits [to lower my time].”

The last U.S. world medal in this event came in 2007, when Brendan Hansen repeated as world champ.

“I had really nothing to lose,” Cordes said of chasing the dominant Peaty, who led by eight tenths at 50 meters.

Peaty, 22, now holds the 11 fastest times ever in the 100m breast, all set since 2015. The next-fastest man all time, Olympic gold and silver medalist Cameron van der Burgh (58.46), opted not to swim the 100m breast at worlds to focus on the 50m breast.

Peaty is the 50m breast favorite. He also holds the world record and is defending champion. The preliminary heats and semifinals are Tuesday, with the final Wednesday in the non-Olympic event. Peaty is not swimming the 200m breast.

Peaty could also be a huge factor in the medley relay on Sunday, where the Great Britain could be the top challenger to the U.S. The Brits took silver at the Rio Games.